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Steve, Auto Service Technician
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Experience:  25+ yrs experience as a professional working technician; ASE L1 master technician
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94 Blazer: blower motor..doesnt work..relay..fuse somewhere

Customer Question

I have a 94 Blazer and the blower motor's high speed doesn't work. I changed the high speed relay and still nothing. Is there a inline fuse somewhere on the car?
Submitted: 11 years ago.
Category: Car
Expert:  Steve replied 11 years ago.
   This could be a failed switch, blower replay, or a fusible link.   Check teh red wire at the blower relay for power; this is a separate power feed from a fusible link that powers up high speed only. 
Steve, Auto Service Technician
Category: Car
Satisfied Customers: 5494
Experience: 25+ yrs experience as a professional working technician; ASE L1 master technician
Steve and 7 other Car Specialists are ready to help you
Customer: replied 11 years ago.
Reply to Steve7654's Post: Stevs,
I checked the power to the red lead at the relay and it is ok. I changed the relay and the switch and srill no high fan speed

                                Thanks,
                                 Harry
Expert:  Steve replied 11 years ago.
 

BLOWER CONTROLS
In all blower speeds except HI, the HTR A/C Fuse supplies current to the Blower Motor. In high speed operation, current from the Blower Switch energizes the High Blower Relay, permitting current to flow from the Battery Junction Block to the Blower Motor.

BLOWER LOW SPEED OPERATION
The Blower Motor operates only in Low Speed through the A/C-Heater Selector Switch. With the A/C-Heater Selector Switch in MAX A/C, NORM A/C, BI-LEVEL, VENT, HEAT or DEFROST, voltage through the A/C-Heater Selector Switch is available to the Blower Resistors through the BRN/WHT (64) wire. The current then flows through all three resistors and the normally closed contacts of the High Blower Relay to the Blower Motor and the Blower Motor runs at Low speed.

BLOWER MEDIUM LOW SPEED OPERATION
With the Blower Switch in M1, current flows from the HTR A/C Fuse, through the A/C-Heater Selector Switch, the BRN/WHT (64) wire and the Blower Switch to the TAN(63) wire at the Blower Resistors. Current then flows through two of the resistors and the normally closed contacts of the High Blower Relay to the Blower Motor. The Blower Motor then runs at Medium Low speed.

BLOWER MEDIUM HIGH SPEED OPERATION
With the Blower Switch in M2, the blower operates the same as in the Medium Low speed, except that the current is directed to the Blower Resistors through the LT BLU (72) wire. Current passes through only one resistor. The Blower Motor then runs at Medium High speed.

BLOWER HIGH SPEED OPERATION
With the Blower Switch in HI, current bypasses the Blower Resistors and flows to the High Blower Relay through the ORN (52) wire. This current energizes the relay and closes the normally open contacts of the relay. Current then flows from the Battery Junction Block through the relay to the Blower Motor, and the Blower Motor runs at High speed.
















Expert:  Steve replied 11 years ago.

Harry;


In high speed position, you should have the following measurements at the high speed blower relay, with the relay plugged in:


Primary side of the relay:


12 volts coming in on the orange wire from the switch


good chassis ground at the black wire


Secondary side of the relay:


12 volts coming into the relay on the red wire from the power distribution junction block


12 volts out on the purple wire to the blower motor.


 


The 5th wire, dark blue in color, leads back to the blower resistor block and is not used in high speed operation, only the other speeds.    When the relay is denergized, the default contact position on the secondary side connects the purple wire to the dark blue wire; this connects the resistor block into the power circuit to the motor, alowing lower speeds to be obtained by switching various resistors into the circuit.


  When the switch is placed in HIGH speed position, the switch supplies power to the relay primary side via the orange wire.   This energizes the relay, which then switches the purple wire connection from the  dark blue one to the red one instead (direct battery power, bypassing all the resistors allowing for maximum speed).

Customer: replied 11 years ago.
Steve,
Thank you so much for the last information. I was able to solve the problem in 10 min. I jumped the red and purple terminals at the relay and the fan came on. I knew then it had to be in the feed circuit. I unpluged the connector in between the relay and the wire harnest and the terminal for the orange wire had burnt open. I jumped the connector and it is working fine. I know this is not a common problem,but you supplied what I needed. You are good!!!
                              Thanks Again,
                                  Harry

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